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BUSY BOLTERS Are you one?  The Shop Area
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Jul 21st, 2025 | | | | Joined: Aug 2004 Posts: 56 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2004 Posts: 56 | 1940 GMC 3/4 ton transmission keeps locking up. I have to remove the shifter unit and somehow get gears back in proper position. Anyone experience this. 4 Speed. | | | | | Joined: Jul 2018 Posts: 51 'Bolter | | 'Bolter Joined: Jul 2018 Posts: 51 | I am not familiar with your particular transmission but is it a "top loader" or does it have "levers" on the side. The gm 3-speed transmission can experience the same type of problem. Sometimes this can be from your linkage not being adjusted properly thus allowing you to put one in gear while the other gear is not fully out of gear. I know its a little confusing but def check your linkage adjustments. | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | If you have the "crash box" 4 speed with the reverse lockout lever on the shifter, those transmissions are pretty flimsy, and are subject to wear. Chances are the shift rails in the top cover are the problem. I'd suggest removing the cover and disassembling the shift rods, looking for wear and/or broken parts such as springs and detent balls. It's also possible for the bearings and shift collars in the main gear set to get worn and hang up while they are being moved in and out of mesh. That box has no synchronizers to give trouble, which can be a good thing!
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Apr 2007 Posts: 1,002 'Bolter | | 'Bolter Joined: Apr 2007 Posts: 1,002 | In addition to problems with shift rails mentioned by Jerry, the shifter guide plate riveted to the shift tower may be worn. The guide plate is made of mild steel and they seem to wear a great deal. To change the guide plate you grind off the rivets holding it to the tower, however, I have never seen a new guide plate for sale, either new or new old stock.
Kent | | | | | Joined: Feb 2001 Posts: 1,096 'Bolter | | 'Bolter Joined: Feb 2001 Posts: 1,096 | I have taken the guide plate off , welded the corner shape and filed it square again , works real good now . I've done 80k miles since and no sign of trouble . | | |
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